US20180375460A1 - Control device of electric motor, electric motor system, and control method of electric motor - Google Patents
Control device of electric motor, electric motor system, and control method of electric motor Download PDFInfo
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- US20180375460A1 US20180375460A1 US16/009,272 US201816009272A US2018375460A1 US 20180375460 A1 US20180375460 A1 US 20180375460A1 US 201816009272 A US201816009272 A US 201816009272A US 2018375460 A1 US2018375460 A1 US 2018375460A1
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- United States
- Prior art keywords
- electric motor
- cooling operation
- control device
- running
- fan
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- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
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Classifications
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02P—CONTROL OR REGULATION OF ELECTRIC MOTORS, ELECTRIC GENERATORS OR DYNAMO-ELECTRIC CONVERTERS; CONTROLLING TRANSFORMERS, REACTORS OR CHOKE COILS
- H02P29/00—Arrangements for regulating or controlling electric motors, appropriate for both AC and DC motors
- H02P29/02—Providing protection against overload without automatic interruption of supply
- H02P29/024—Detecting a fault condition, e.g. short circuit, locked rotor, open circuit or loss of load
- H02P29/028—Detecting a fault condition, e.g. short circuit, locked rotor, open circuit or loss of load the motor continuing operation despite the fault condition, e.g. eliminating, compensating for or remedying the fault
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02P—CONTROL OR REGULATION OF ELECTRIC MOTORS, ELECTRIC GENERATORS OR DYNAMO-ELECTRIC CONVERTERS; CONTROLLING TRANSFORMERS, REACTORS OR CHOKE COILS
- H02P29/00—Arrangements for regulating or controlling electric motors, appropriate for both AC and DC motors
- H02P29/60—Controlling or determining the temperature of the motor or of the drive
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02K—DYNAMO-ELECTRIC MACHINES
- H02K9/00—Arrangements for cooling or ventilating
- H02K9/02—Arrangements for cooling or ventilating by ambient air flowing through the machine
- H02K9/04—Arrangements for cooling or ventilating by ambient air flowing through the machine having means for generating a flow of cooling medium
- H02K9/06—Arrangements for cooling or ventilating by ambient air flowing through the machine having means for generating a flow of cooling medium with fans or impellers driven by the machine shaft
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02P—CONTROL OR REGULATION OF ELECTRIC MOTORS, ELECTRIC GENERATORS OR DYNAMO-ELECTRIC CONVERTERS; CONTROLLING TRANSFORMERS, REACTORS OR CHOKE COILS
- H02P29/00—Arrangements for regulating or controlling electric motors, appropriate for both AC and DC motors
- H02P29/02—Providing protection against overload without automatic interruption of supply
- H02P29/032—Preventing damage to the motor, e.g. setting individual current limits for different drive conditions
Definitions
- the present invention relates to a control device of an electric motor, an electric motor system, and a control method of an electric motor.
- a technology is known that detects an abnormality in a fan which cools an electric motor (as disclosed in JP 2017-073943 A, for example).
- a control device of an electric motor in which a fan is installed includes a cooling operation information acquisition section configured to acquire cooling operation information of the fan; a cooling operation determination section configured to determine whether or not the cooling operation information indicates a normal cooling operation; a running information acquisition section configured to acquire running information of the electric motor; and a running control section configured to control the running of the electric motor so as to be in an overheat-prevented state, with reference to the running information, when it is determined that the cooling operation information does not indicate a normal cooling operation.
- a method of controlling an electric motor in which a fan is installed includes acquiring cooling operation information of the fan; determining whether or not the cooling operation information indicates a normal cooling operation; acquiring running information of the electric motor; and controlling the running of the electric motor so as to be in an overheat-prevented state, with reference to the running information, when it is determined that the cooling operation information does not indicate a normal cooling operation.
- the operation of the electric motor can continue so as not to be in an overheated state.
- a work e.g., machining
- FIG. 1 is a block diagram of an electric motor system according to an embodiment
- FIG. 2 is a cross-sectional view of an electric motor according to an embodiment
- FIG. 3 is a cross-sectional view of a fan according to an embodiment
- FIG. 4 is a flowchart showing an example of an operation flow of the electric motor system
- FIG. 5 is a flowchart showing an example of the flow of step S 12 in FIG. 4 ;
- FIG. 6 is a graph showing a relationship between a temperature of the electric motor and time, in which the vertical axis indicates the temperature, while the horizontal axis indicates the time;
- FIG. 7 is a graph showing a relationship between the temperature of the electric motor and time, and a relationship between a current value of the electric motor and time, in which the vertical axis indicates the temperature and the current value, while the horizontal axis indicates the time;
- FIG. 8 is a block diagram of an electric motor system according to another embodiment.
- FIG. 9 is a block diagram of a control device according to another embodiment.
- the axial direction indicates a direction along a rotational axis O ( FIG. 2 ) of an electric motor
- the radial direction indicates a direction of a radius of a circle centered about the axis O
- the circumferential direction indicates a direction of a circumference of the circle.
- the left direction in FIG. 2 is referred to as a forward direction.
- the electric motor system 10 includes an electric motor 12 , a fan 14 , a warning output section 16 , a power source 18 , and a control device 20 .
- the electric motor 12 includes a rotor 22 , a stator 24 , a housing 26 , a bearing 28 , a bearing 30 , a rear cover 32 , a terminal box 34 , and a first temperature detection section 35 .
- the stator 24 is made of e.g. a plurality of magnetic steel sheets laminated in the axial direction.
- a coil 36 is wound around the stator 24 .
- a power cable 37 is led out from the coil 36 , is wired so as to be drawn into the terminal box 34 , and is electrically connected to the control device 20 .
- the first temperature detection section 35 is installed on an outer peripheral surface of the stator 24 (or the coil 36 ).
- the first temperature detection section 35 includes e.g. a thermocouple, a thermopile, a thermistor, or a platinum resistance temperature detector, and measures the temperature at a location at which the first temperature detection section 35 is installed.
- a signal cable 39 is connected to the first temperature detection section 35 , is wired so as to be drawn into the terminal box 34 , and is electrically connected to the control device 20 .
- the first temperature detection section 35 transmits information of the detected temperature to the control device 20 , as running information of the electric motor 12 .
- the rotor 22 includes a rotary shaft 38 , and a rotor core 40 fixed to the radially outside of the rotary shaft 38 .
- the rotor core 40 is disposed so as to be slightly separated radially inward from the stator 24 .
- the housing 26 supports the stator 24 .
- the housing 26 includes a front housing 42 fixed axially front side of the stator 24 , and a rear housing 44 fixed axially rear side of the stator 24 .
- the front housing 42 is fixed to an axially front end face 24 a of the stator 24 .
- the rear housing 44 includes an annular main body 46 fixed to an axially rear end face 24 b of the stator 24 , and an annular bearing support 48 fixed radially inside of the main body 46 .
- the rear cover 32 is fixed to an axially rear end of the main body 46 of the rear housing 44 .
- a plurality of through holes are formed at an axially rear wall 32 a of the rear cover 32 .
- the rotor core 40 of the rotor 22 is housed in an interior space S 1 defined by the front housing 42 , the rear housing 44 , the stator 24 , and the rear cover 32 .
- the bearing 28 is interposed between a radially inside end face 42 a of the front housing 42 and the rotary shaft 38 , and rotatably supports the rotary shaft 38 .
- the bearing 30 is interposed between the bearing support portion 48 of the rear housing 44 and the rotary shaft 38 , and rotatably supports the rotary shaft 38 similarly to the bearing 28 .
- the terminal box 34 is fixed on the outer peripheral surface of the rear housing 44 .
- the power cable 37 which supplies power to the coil 36 of the electric motor 12 , is drawn into the terminal box 34 .
- a power cable 61 FIG. 3
- a signal cable 74 FIG. 3
- the power cable 61 of the fan 14 and the signal cable 74 will be described later.
- the fan 14 is installed inside the rear cover 32 of the electric motor 12 , and is disposed axially rearward of the stator 24 and the rotor 22 , so as to be centered about the axis O.
- the fan 14 includes the fan motor 50 , a rotary body 51 , and the second temperature detection section 52 .
- the fan motor 50 includes a fan stator 54 , a fan rotor 56 rotatably arranged radially inside of the fan stator 54 , and a fan housing 58 that supports the fan stator 54 .
- a coil 60 is wound around the fan stator 54 .
- the power cable 61 is led out from the coil 60 , is wired so as to be drawn into the terminal box 34 , and is electrically connected to the power source 18 .
- the fan rotor 56 includes a rotary shaft 62 , and a rotor core 64 fixed to the radially outside of the rotary shaft 62 .
- the rotary shaft 62 is supported by bearings 66 and 68 so as to be able to rotate about the axis O.
- the fan housing 58 is hollow and defines an interior space S 2 .
- the fan stator 54 and the rotor core 64 are housed in the interior space S 2 .
- the bearings 66 and 68 are fixed to the fan housing 58 .
- the rotary shaft 62 protrudes axially front ward from the fan housing 58 through a through hole 58 b formed at an axially front wall 58 a of the fan housing 58 .
- the rotary body 51 includes an annular portion 70 , and a plurality of vanes 72 fixed to the radially outside of the annular portion 70 .
- the annular portion 70 is fixed to the axially front end of the rotary shaft 62 .
- the plurality of vanes 72 are disposed so as to align in the circumferential direction at substantially equal intervals.
- the second temperature detection section 52 is installed on the coil 60 .
- the second temperature detection section 52 has a thermocouple, a thermopile, a thermistor, or a platinum resistance temperature detector, and measures the temperature at a location at which the second temperature detection section 52 is installed.
- the signal cable 74 is connected to the second temperature detection section 52 .
- the signal cable 74 is wired so as to be drawn into the terminal box 34 , together with the power cable 61 of the fan motor 50 .
- the signal cable 74 is electrically connected to the control device 20 .
- the second temperature detection section 52 transmits information of the detected temperature to the control device 20 , as cooling operation information of the fan 14 .
- the power source 18 is e.g. a commercial AC power source, and applies an AC voltage of a predetermined frequency to the coil 60 of the fan 14 , via the power cable 61 .
- the fan rotor 56 and the rotary body 51 are rotated integrally at a predetermined rotation speed R Ref .
- the warning output section 16 includes e.g. a speaker or a display, and outputs a sound or an image in accordance with a command from the control device 20 .
- the control device 20 controls the electric motor 12 .
- the control device 20 includes a cooling operation information acquisition section 76 , a cooling operation determination section 78 , a running information acquisition section 80 , a running control section 82 , a warning signal generation section 84 , and a running determination section 86 .
- the control device 20 may be configured by a single computer having a processor and a memory (RAM, ROM, etc.).
- the processor of the control device 20 functions as the cooling operation information acquisition section 76 , the cooling operation determination section 78 , the running information acquisition section 80 , the running control section 82 , the warning signal generation section 84 , and the running determination section 86 .
- control device 20 may be configured by a plurality of computers, each of which has a processor and a memory (RAM, ROM, etc.).
- the respective processors of the plurality of computers may function as the respective cooling operation information acquisition section 76 , the cooling operation determination section 78 , the running information acquisition section 80 , the running control section 82 , the warning signal generation section 84 , and the running determination section 86 .
- cooling operation information acquisition section 76 the cooling operation determination section 78 , the running information acquisition section 80 , the running control section 82 , the warning signal generation section 84 , and the running determination section 86 will be described later.
- the flow illustrated in FIG. 4 is started when the control device 20 receives an operation start command from an operator or a host controller.
- Step S 1 the control device 20 starts to run the electric motor 12 .
- the control device 20 causes the electric motor 12 to operate in a normal running mode.
- the control device 20 sends a current value command I 1 to the electric motor 12 , and the electric motor 12 outputs a rotational force P 1 in accordance with the current value command I 1 .
- the current value command I 1 sent by the control device 20 in the normal running mode is set by the operator or by a computer program. In this way, the control device 20 operates the electric motor 12 in the normal running mode.
- Step S 2 the control device 20 or the operator starts to operate the fan 14 .
- the control device 20 is connected to the power source 18 so as to control the ON/OFF of the power source 18 .
- the control device 20 transmits a command to the power source 18 so as to turn ON the power source 18 .
- the operator manually turns ON the power source 18 .
- the power source 18 When the power source 18 is turned ON, the power source 18 supplies the AC voltage of the predetermined frequency to the coil 60 of the fan 14 . As a result, the fan 14 rotates at the predetermined rotation speed R Ref , and an airflow is generated in the electric motor 12 . By this airflow, each component of the electric motor 12 is cooled.
- Step S 3 the control device 20 starts to acquire the running information of the electric motor 12 . Specifically, the control device 20 transmits a temperature detection command to the first temperature detection section 35 provided in the electric motor 12 .
- the first temperature detection section 35 When the first temperature detection section 35 receives the temperature detection command, it repeatedly detects a temperature T 1 at the location at which it is installed, and sequentially transmits the information of the detected temperature T 1 to the control device 20 via the signal cable 39 , as the running information of the electric motor 12 .
- the control device 20 sequentially stores in the memory the temperature T 1 received from the first temperature detection section 35 .
- the temperature T 1 detected at this time is one item of information indicative of the running state of the electric motor 12 in operation (i.e., the running information).
- the control device 20 functions as the running information acquisition section 80 ( FIG. 1 ) configured to acquire the running information of the electric motor 12 .
- Step S 4 the control device 20 starts to acquire the cooling operation information of the fan 14 . Specifically, the control device 20 transmits a temperature detection command to the second temperature detection section 52 provided in the fan 14 .
- the second temperature detection section 52 When the second temperature detection section 52 receives the temperature detection command, it repeatedly detects a temperature T 2 at the location at which it is installed, and sequentially transmits the information of the detected temperature T 2 to the control device 20 via the signal cable 74 , as the cooling operation information of the fan 14 .
- the control device 20 sequentially stores in the memory the temperature T 2 received from the second temperature detection section 52 .
- the temperature T 2 detected at this time is one item of the information indicative of the cooling operation state of the working fan 14 in operation (i.e., the cooling operation information). More specifically, as the electric motor 12 operates, the rotation of the rotary body 51 or the fan rotor 56 of the fan 14 may possibly be obstructed, due to which, the rotation speed of the fan 14 may decrease from the rotation speed R Ref .
- Such obstruction of the rotation of the rotary body 51 or the fan rotor 56 may be caused e.g. by a foreign material, such as cutting fluid, attaching to the rotary body 51 or the fan rotor 56 during operation of the electric motor 12 .
- the control device 20 functions as the cooling operation information acquisition section 76 ( FIG. 1 ) configured to acquire the cooling operation information of the fan 14 .
- the control device 20 determines whether or not the cooling operation information of the fan 14 indicates a normal cooling operation. Specifically, the control device 20 determines whether or not the temperature T 2 most-recently acquired from the second temperature detection section 52 is lower than a threshold value T 2 ⁇ (i.e., T 2 ⁇ T 2 ⁇ ).
- the threshold value T 2 ⁇ is predetermined by the operator, and is stored in the memory of the control device 20 .
- the control device 20 determines that the cooling operation information of the fan 14 indicates the normal cooling operation (i.e., determines YES), and proceeds to Step S 6 .
- the control device 20 determines that the cooling operation information of the fan 14 does not indicate the normal cooling operation (i.e., determines NO), and proceeds to Step S 7 .
- the control device 20 functions as the cooling operation determination section 78 ( FIG. 1 ) configured to determine whether or not the cooling operation information indicates the normal cooling operation.
- the control device 20 determines whether or not it receives an operation end command from the operator or the host controller. If the control device 20 determines that it receives the operation end command (i.e., determines YES), the control device 20 transmits a stop command to the electric motor 12 , sets the current value supplied to the electric motor 12 to zero. Thereby, the operation of the electric motor 12 is stopped.
- control device 20 determines that it does not receive the operation end command (i.e., determines NO)
- the control device 20 returns to Step S 5 .
- the control device 20 notifies to the operator via the warning output section 16 that an abnormality occurs in the cooling operation of the fan 14 . Specifically, the control device 20 generates the warning signal in the form of a voice signal or an image signal. Then, the control device 20 transmits the generated warning signal to the warning output section 16 .
- the warning output section 16 outputs the warning sound or the warning image in accordance with the received warning signal via the speaker or the display portion. In this way, the operator can recognize that an abnormality has occurred in the cooling operation of the fan 14 .
- the control device 20 functions as the warning signal generation section 84 ( FIG. 1 ) configured to generate the warning signal.
- the control device 20 determines whether or not the running information of the electric motor 12 indicates the normal running of the electric motor 12 . Specifically, the control device 20 determines whether or not the temperature T 1 most-recently acquired from the first temperature detection section 35 is lower than a threshold value T 1 ⁇ , (i.e., T 1 ⁇ T 1 ⁇ ).
- the threshold value T 1 ⁇ is predetermined by the operator, and is stored in the memory of the control device 20 .
- the threshold value T 1 ⁇ is set as a threshold value defining a boundary to determine whether the electric motor 12 is in an overheated state. In this case, when the temperature T 1 is equal to or greater than the threshold value T 1 ⁇ , (i.e., T 1 ⁇ T 1 ⁇ ), the electric motor 12 is considered to be overheating.
- Step S 10 the control device 20 determines that the running information of the electric motor 12 indicates the normal running (i.e., determines YES), and proceeds to Step S 10 .
- the control device 20 determines that the running information of the electric motor 12 does not indicate normal running (i.e., determines NO), and proceeds to Step S 9 .
- control device 20 functions as the running determination section 86 ( FIG. 1 ) configured to determine whether the running information of the electric motor 12 indicates normal running.
- Step S 9 the control device 20 stops the operation of the electric motor 12 . Specifically, the control device 20 transmits the stop command to the electric motor 12 , and sets the current value supplied to the electric motor 12 to zero. In this way, the operation of the electric motor 12 is stopped. Then, the control device 20 ends the flow illustrated in FIG. 4 .
- Step S 10 the control device 20 acquires first data indicating a possibility that the electric motor 12 is in an overheated state.
- first data indicating a possibility that the electric motor 12 is in an overheated state.
- a one-dot chain line 90 in FIG. 6 indicates a relationship between a time t and the temperature T 1 when the cooling operation of the fan 14 is normal and the electric motor 12 is run at a rated current value.
- the temperature T 1 increases with time and approaches asymptotically to a predetermined saturation temperature T 1 ( ⁇ T 1 ⁇ ).
- a two-dot chain line 92 in FIG. 6 indicates a relationship between the time t and the temperature T 1 when an abnormality occurs in the cooling operation of the fan 14 but the electric motor 12 is run at a current value that is significantly smaller than the rated current value.
- the temperature T 1 of the electric motor 12 reaches saturation at a temperature that is significantly lower than the saturation temperature T 1 ⁇ .
- a broken line 94 in FIG. 6 indicates a relationship between the time t and the temperature T 1 when an abnormality occurs in the cooling operation of the fan 14 at a time point t 1 during the fan 14 is run at the rated current value, and the electric motor 12 continues to be run at the rated current value even after the abnormality occurs.
- the control device 20 acquires the first data in order to quantitatively evaluate the possibility that the running of the electric motor 12 is in an overheated state.
- This degree of increase ⁇ T 1 / ⁇ t corresponds to a gradient of the graph shown in FIG. 6 .
- the gradient of the relationship 94 is significantly greater than the other relationships 90 and 92 after the time point t 1 . Therefore, the degree of increase ⁇ T 1 / ⁇ t can be used as the first data ⁇ T 1 / ⁇ t indicating the possibility that the running of the electric motor 12 is in an overheated state.
- Step S 11 on the basis of the first data ( ⁇ 1 , ⁇ T 1 / ⁇ t) acquired at Step S 10 , the control device 20 determines whether or not the possibility that the running of the electric motor 12 is in an overheated state is high.
- the control device 20 determines whether or not the first data ⁇ 1 is equal to or less than a threshold value ⁇ (i.e., ⁇ 1 ⁇ ).
- the threshold value ⁇ is predetermined by the operator, and is stored in the memory of the control device 20 .
- Step S 12 the control device 20 determines that the possibility that the running of the electric motor 12 is in an overheated state is high (i.e., determines YES), and proceeds to Step S 12 .
- the control device 20 determines that the possibility that the running of the electric motor 12 is in an overheated state is low (i.e., determines NO), returns to the above-described Step S 6 , and continues running the electric motor 12 in the normal running mode until it determines YES at Step S 6 .
- the control device 20 determines whether or not the first data ⁇ T 1 / ⁇ t is equal to or greater than a threshold value ⁇ (i.e., ⁇ T 1 / ⁇ t ⁇ ).
- the threshold value ⁇ is predetermined by the operator, and is stored in the memory of the control device 20 .
- the control device 20 determines YES when ⁇ T 1 / ⁇ t ⁇ is satisfied, and proceeds to Step S 12 . On the other hand, the control device 20 determines NO when ⁇ T 1 / ⁇ t ⁇ is satisfied, and returns to the above-described Step S 6 .
- the control device 20 may determine the possibility of the electric motor 12 being in an overheated state, on the basis of ⁇ 1 and ⁇ T 1 / ⁇ t. For example, the control device 20 may determine YES when ⁇ 1 ⁇ or ⁇ T 1 / ⁇ t ⁇ , while determining NO when ⁇ 1 ⁇ and ⁇ T 1 / ⁇ t ⁇ .
- Step S 12 the control device 20 runs the electric motor 12 in an abnormal running mode. This Step S 12 will be described with reference to FIG. 5 . After beginning Step S 12 , at Step S 21 , the control device 20 reduces the output of the electric motor 12 .
- the control device 20 changes the current value command transmitted to the electric motor 12 from the current value command I 1 to a second current value command I 2 , and sends the second current value command I 2 to the electric motor 12 .
- the second current value command I 2 is for running the electric motor 12 at a lower current value than the current value command I 1 .
- the electric motor 12 outputs a second rotational force P 2 ( ⁇ P 1 ) in accordance with the second current value command I 2 .
- the control device 20 acquires second data in order to quantitatively evaluate a possibility that the temperature T 1 of the electric motor 12 exceeds the saturation temperature T 1 ⁇ .
- control device 20 may calculate both ⁇ 2 and ⁇ T 1 / ⁇ t as the second data.
- the control device 20 acquires the second data ( ⁇ 2 , ⁇ T 1 / ⁇ t) and stores it in the memory.
- Step S 23 on the basis of the second data ( ⁇ 2 , ⁇ T 1 / ⁇ t) acquired at Step S 22 , the control device 20 determines whether or not the possibility that the temperature T 1 exceeds the saturation temperature T 1 ⁇ is high.
- the control device 20 determines whether or not the second data ⁇ 2 is equal to or less than a threshold value ⁇ (i.e., ⁇ 2 ⁇ ).
- the threshold value ⁇ is predetermined by the operator, and is stored in the memory of the control device 20 .
- Step S 21 the control device 20 determines that the possibility of the temperature T 1 exceeding the saturation temperature T 1 ⁇ is high (i.e., determines YES), and returns to Step S 21 .
- the control device 20 determines that the possibility of the temperature T 1 exceeding the saturation temperature T 1 ⁇ is low (i.e., determines NO), and proceeds to Step S 24 .
- the control device 20 determines whether or not the second data ⁇ T 1 / ⁇ t is equal to or greater than a threshold value ⁇ (i.e., ⁇ T 1 / ⁇ t ⁇ ).
- the threshold value ⁇ is predetermined by the operator, and is stored in the memory of the control device 20 . It should be noted that the threshold value ⁇ may be the same as or different from the above-described threshold value ⁇ .
- the control device 20 determines YES when ⁇ T 1 / ⁇ t ⁇ is satisfied, and returns to Step S 21 . On the other hand, the control device 20 determines NO when ⁇ T 1 / ⁇ t ⁇ is satisfied, and proceeds to Step S 24 .
- the control device 20 may determine the possibility of the temperature T 1 exceeding the saturation temperature T 1 ⁇ on the basis of ⁇ 2 and ⁇ T 1 / ⁇ t. For example, the control device 20 may determine YES when ⁇ 2 ⁇ or ⁇ T 1 / ⁇ t ⁇ , while determining NO when ⁇ 2 > ⁇ and ⁇ T 1 / ⁇ t ⁇ .
- control device 20 repeats Step S 21 to Step S 23 until it determines NO at Step S 23 .
- the control device 20 reduces the output of the electric motor 12 in a stepwise manner each time the control device 20 executes Step S 21 .
- the control device 20 reduces the current value I of the electric motor 12 from the current value I 1 to the current value I 2 (carrying out Step S 21 for a first time). Then, at a time point t 3 , the control device 20 further reduces the current value I of the electric motor 12 from the current value I 2 to a current value I 3 (carrying out Step S 21 for a second time).
- the control device 20 controls the current value I of the electric motor 12 with reference to the temperature T 1 and the saturation temperature T 1 ⁇ . Due to this, as shown by the relationship 96 in FIG. 7 , the temperature T 1 of the electric motor 12 approaches asymptotically to the saturation temperature T 1 ⁇ so as not to exceed the saturation temperature T 1 ⁇ , as a result of which, overheating by exceeding the saturation temperature T 1 ⁇ is prevented.
- control device 20 functions as the running control section 82 ( FIG. 1 ) configured to control the running of the electric motor 12 with reference to the running information (the temperature T 1 ) so as to be in an overheat-prevented state.
- Step S 24 similarly to the above-described Step S 6 , the control device 20 determines whether it receives the operation end command.
- the control device 20 determines YES, the control device 20 stops the running of the electric motor 12 (and the power source 18 ), ends Step S 12 illustrated in FIG. 5 , and thus ends the flow illustrated in FIG. 4 .
- the control device 20 determines NO, the control device 20 returns to step S 23 .
- the control device 20 controls the running of the electric motor 12 so as to be in the overheat-prevented state with reference to the running information (the temperature T 1 ) of the electric motor 12 , when the control device 20 determines that the cooling operation information (the temperature T 2 ) of the fan 14 does not indicate the normal cooling operation (i.e., determines NO at Step S 5 ).
- control device 20 determines NO at Step S 5 , the control device 20 generates the warning signal for notifying the abnormality in the cooling operation of the fan 14 , and notifies the operator. According to this configuration, the operator can reliably recognize that an abnormality has occurred in the fan 14 .
- the control device 20 acquires the temperature T 2 detected by the second temperature detection section 52 as the cooling operation information of the fan 14 . As described above, since there is a high degree of correlation between the temperature T 2 and the cooling operation state of the fan 14 , the control device 20 can determine whether the cooling operation of the fan 14 is normal with using the temperature T 2 in a quantitative and highly accurate manner, at Step S 5 .
- the control device 20 determines whether the running information (the temperature T 1 ) of the electric motor 12 is normal (Step S 8 ), and the control device 20 stops the operation of the electric motor 12 (Step S 9 ) if it determines that the running information is not normal (i.e., determines NO at Step S 8 ). According to this configuration, overheating of the electric motor 12 can be reliably detected, and it is possible to immediately stop the operation of the electric motor 12 .
- the control device 20 controls the operation of the electric motor 12 such that the temperature T 1 of the electric motor 12 does not exceed the saturation temperature T 1 ⁇ .
- the electric motor 12 can be reliably prevented from overheating, and the output of the electric motor 12 can be increased to a maximum within a range in which the overheat-prevented state of the electric motor 12 is maintained.
- the output of the electric motor 12 can be increased to a maximum within a range in which the overheat-prevented state of the electric motor 12 is maintained.
- the control device 20 carries out the abnormal running mode at Step S 12 only when it determines YES at Step S 11 .
- the electric motor 12 can be operated in the normal running mode such that the output of the electric motor 12 can be prevented from decreasing excessively when the possibility of the overheated state is low (e.g., in the case of the relationship 92 in FIG. 6 ).
- the electric motor system 100 is different from the above-described electric motor system 10 in a fan 102 .
- the fan 102 according to this embodiment is different from the above-described fan 14 in that the fan 102 includes a rotation detection section 104 instead of the second temperature detection section 52 .
- the rotation detection section 104 includes e.g. an encoder or a Hall element, and measures the rotation speed of the fan 102 . Specifically, the rotation detection section 104 is disposed in the vicinity of the fan rotor 56 or the rotary body 51 of the fan 102 , and measures the rotation speed of the fan rotor 56 or the rotary body 51 . The rotation detection section 104 transmits, as cooling operation information of the fan 102 , the information of the detected rotation speed to the control device 20 via the signal cable 74 .
- the control device 20 of the electric motor system 100 carries out the operation flow illustrated in FIG. 4 and FIG. 5 .
- the operation flow of the electric motor system 100 differs from the above-described embodiment in Steps S 4 and S 5 .
- the control device 20 functions as the cooling operation information acquisition section 76 , and starts to acquire the cooling operation information of the fan 102 . Specifically, the control device 20 transmits a rotation detection command to the rotation detection section 104 provided in the fan 102 .
- the rotation detection section 104 When the rotation detection section 104 receives the rotation detection command, the rotation detection section 104 repeatedly (e.g., at a cycle ⁇ 3 ) measures a rotation speed R of the fan 102 , and sequentially transmits, as the cooling operation information of the fan 102 , the information of the detected rotation speed R to the control device 20 via the signal cable 74 .
- the control device 20 sequentially stores the rotation speed R received from the rotation detection section 104 in the memory.
- the rotation speed R of the fan 102 is proportional to the airflow generated by the fan 102 in the electric motor 12 , there is a high correlation between the rotation speed R and the cooling operation state of the fan 102 . Therefore, the rotation speed R can be used as the information indicating the cooling operation state of the working fan 102 (i.e., the cooling operation information).
- the control device 20 functions as the cooling operation determination section 78 , and determines whether or not the cooling operation information of the fan 102 indicates the normal cooling operation. Specifically, the control device 20 determines whether or not the rotation speed R most-recently acquired from the rotation detection section 104 is higher than a threshold value R ⁇ (i.e., R>R ⁇ ).
- the threshold value R ⁇ is predetermined by the operator as a value lower than the above-described rotation speed R Ref (i.e., R ⁇ >R Ref ), and is stored in the memory of the control device 20 .
- R ⁇ the control device 20 determines that the cooling operation information of the fan 102 indicates the normal cooling operation (i.e., determines YES), and proceeds to Step S 6 .
- Step S 5 the control device 20 sequentially carries out Step S 6 to Step S 12 , similarly as the above-described embodiment.
- the control device 20 acquires the rotation speed R detected by the rotation detection section 104 as the cooling operation information of the fan 102 .
- the control device 20 can determine whether the cooling operation of the fan 102 is normal with using the rotation speed R in a quantitative and highly accurate manner, at Step S 5 .
- the warning signal generation section 84 and the running determination section 86 can be omitted from the above-described control device 20 .
- Such a control device 110 is illustrated in FIG. 9 .
- the control device 110 includes a cooling operation information acquisition section 112 , a cooling operation determination section 114 , a running information acquisition section 116 , and a running control section 118 .
- the control device 110 can be configured by a single computer having a processor and a memory (RAM, ROM, etc.).
- the processor of the control device 110 functions as the cooling operation information acquisition section 112 , the cooling operation determination section 114 , the running information acquisition section 116 , and the running control section 118 .
- control device 110 may be configured by a plurality of computers, each having a processor and a memory (RAM, ROM, etc.).
- the respective processors of the plurality of computers may functions as the respective cooling operation information acquisition section 112 , the cooling operation determination section 114 , the running information acquisition section 116 , and the running control section 118 .
- the cooling operation information acquisition section 112 acquires the cooling operation information of the fan 14 , 102 (e.g., the temperature T 2 or the rotation speed R).
- the cooling operation determination section 114 determines whether or not the cooling operation information indicates the normal cooling operation. For example, similarly to the above-described embodiment, the cooling operation determination section 114 determines whether the cooling operation information indicates the normal cooling operation by comparing the cooling operation information with a predetermined threshold value.
- the running information acquisition section 116 acquires the running information (e.g., the temperature T 1 ) of the electric motor 12 .
- the running control section 118 controls the running of the electric motor 12 so as to be in the overheat-prevented state with reference to the running information acquired by the running information acquisition section 116 .
- the running control section 118 controls the running of the electric motor 12 to be in the overheat-prevented state by reducing the output (e.g., the current value) of the electric motor 12 with reference to the running information.
- the above-described first temperature detection section 35 may be disposed at any location in the electric motor 12 . Further, the first temperature detection section 35 of the electric motor 12 may be omitted, wherein the cooling operation information acquisition section 76 , 112 may acquire, as the running information of the electric motor 12 , a feedback (a feedback current, a load torque, etc.) of the electric motor 12 , instead of the above-described temperature T 1 . In this case, at Step S 8 , the control device 20 , 110 compares the acquired feedback with a threshold value ⁇ and determines whether the operation of the electric motor 12 is normal (i.e., whether it is in an overheated state).
- This threshold value ⁇ can be set as a feedback transmitted from the electric motor 12 when the electric motor 12 is in the overheated state. Further, in this case, at Step S 10 and Step S 22 , the control device 20 , 110 acquires the first data and the second data that are based on the feedback of the electric motor 12 .
- the power source 18 may not necessarily be a commercial AC power source, and may be a power source having an inverter therein, which is capable of controlling the frequency.
- the warning output section 16 is provided separate from the control device 20 , but may alternatively be incorporated in the control device 20 .
- the control device 20 may include the display or the speaker.
- control device 20 , 110 may increase the output (the current value command I) of the electric motor 12 after Step S 23 in FIG. 5 . Further, the control device 20 , 110 may send a voltage value command or a power value command to the electric motor 12 , instead of the current value command I. In this case, the control device 20 , 110 reduces the voltage value command or the power value command at step S 21 in FIG. 5 .
- the fan 14 is installed inside the rear cover 32 axially rearward of the stator 24 and the rotor 22 of the electric motor 12 .
- the fan 14 may be installed at any position where the fan 14 can cool the electric motor 12 .
- the fan 14 is not limited to the axial fan illustrated in FIG. 3 , but may be any type of fan, such as a centrifugal fan, which can generate an airflow.
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Abstract
Description
- The present invention relates to a control device of an electric motor, an electric motor system, and a control method of an electric motor.
- A technology is known that detects an abnormality in a fan which cools an electric motor (as disclosed in JP 2017-073943 A, for example).
- In related art, it is desirable to continue to run the electric motor as long as possible, even if an abnormality occurs in a fan motor.
- In an aspect of the present disclosure, a control device of an electric motor in which a fan is installed, includes a cooling operation information acquisition section configured to acquire cooling operation information of the fan; a cooling operation determination section configured to determine whether or not the cooling operation information indicates a normal cooling operation; a running information acquisition section configured to acquire running information of the electric motor; and a running control section configured to control the running of the electric motor so as to be in an overheat-prevented state, with reference to the running information, when it is determined that the cooling operation information does not indicate a normal cooling operation.
- In another aspect of the present disclosure, a method of controlling an electric motor in which a fan is installed, includes acquiring cooling operation information of the fan; determining whether or not the cooling operation information indicates a normal cooling operation; acquiring running information of the electric motor; and controlling the running of the electric motor so as to be in an overheat-prevented state, with reference to the running information, when it is determined that the cooling operation information does not indicate a normal cooling operation.
- According to this disclosure, even if a temporary abnormality occurs in the cooling operation of the fan, the operation of the electric motor can continue so as not to be in an overheated state. As a result, it is possible to avoid completely stopping a work (e.g., machining) in which the
electric motor 12 is being used, and the operator can repair or replace thefan 14 at a desired timing that will not obstruct the operation. -
FIG. 1 is a block diagram of an electric motor system according to an embodiment; -
FIG. 2 is a cross-sectional view of an electric motor according to an embodiment; -
FIG. 3 is a cross-sectional view of a fan according to an embodiment; -
FIG. 4 is a flowchart showing an example of an operation flow of the electric motor system; -
FIG. 5 is a flowchart showing an example of the flow of step S12 inFIG. 4 ; -
FIG. 6 is a graph showing a relationship between a temperature of the electric motor and time, in which the vertical axis indicates the temperature, while the horizontal axis indicates the time; -
FIG. 7 is a graph showing a relationship between the temperature of the electric motor and time, and a relationship between a current value of the electric motor and time, in which the vertical axis indicates the temperature and the current value, while the horizontal axis indicates the time; -
FIG. 8 is a block diagram of an electric motor system according to another embodiment; and -
FIG. 9 is a block diagram of a control device according to another embodiment. - Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. It should be noted that, in the various embodiments described below, similar elements are assigned the same reference numerals, and redundant explanations thereof will be omitted. Further, in the following explanation, the axial direction indicates a direction along a rotational axis O (
FIG. 2 ) of an electric motor, the radial direction indicates a direction of a radius of a circle centered about the axis O, and the circumferential direction indicates a direction of a circumference of the circle. In addition, for convenience, the left direction inFIG. 2 is referred to as a forward direction. - With reference to
FIG. 1 toFIG. 3 , anelectric motor system 10 according to an embodiment will be described. Theelectric motor system 10 includes anelectric motor 12, afan 14, awarning output section 16, apower source 18, and acontrol device 20. - As illustrated in
FIG. 2 , theelectric motor 12 includes arotor 22, astator 24, ahousing 26, abearing 28, abearing 30, arear cover 32, aterminal box 34, and a firsttemperature detection section 35. Thestator 24 is made of e.g. a plurality of magnetic steel sheets laminated in the axial direction. - A
coil 36 is wound around thestator 24. Apower cable 37 is led out from thecoil 36, is wired so as to be drawn into theterminal box 34, and is electrically connected to thecontrol device 20. - In this embodiment, the first
temperature detection section 35 is installed on an outer peripheral surface of the stator 24 (or the coil 36). The firsttemperature detection section 35 includes e.g. a thermocouple, a thermopile, a thermistor, or a platinum resistance temperature detector, and measures the temperature at a location at which the firsttemperature detection section 35 is installed. - A
signal cable 39 is connected to the firsttemperature detection section 35, is wired so as to be drawn into theterminal box 34, and is electrically connected to thecontrol device 20. The firsttemperature detection section 35 transmits information of the detected temperature to thecontrol device 20, as running information of theelectric motor 12. - The
rotor 22 includes arotary shaft 38, and arotor core 40 fixed to the radially outside of therotary shaft 38. Therotor core 40 is disposed so as to be slightly separated radially inward from thestator 24. - The
housing 26 supports thestator 24. Specifically, thehousing 26 includes afront housing 42 fixed axially front side of thestator 24, and arear housing 44 fixed axially rear side of thestator 24. Thefront housing 42 is fixed to an axiallyfront end face 24 a of thestator 24. - The
rear housing 44 includes an annularmain body 46 fixed to an axially rear end face 24 b of thestator 24, and anannular bearing support 48 fixed radially inside of themain body 46. - The
rear cover 32 is fixed to an axially rear end of themain body 46 of therear housing 44. A plurality of through holes (not illustrated) are formed at an axiallyrear wall 32 a of therear cover 32. Therotor core 40 of therotor 22 is housed in an interior space S1 defined by thefront housing 42, therear housing 44, thestator 24, and therear cover 32. - The
bearing 28 is interposed between a radially insideend face 42 a of thefront housing 42 and therotary shaft 38, and rotatably supports therotary shaft 38. Thebearing 30 is interposed between thebearing support portion 48 of therear housing 44 and therotary shaft 38, and rotatably supports therotary shaft 38 similarly to thebearing 28. - The
terminal box 34 is fixed on the outer peripheral surface of therear housing 44. Thepower cable 37, which supplies power to thecoil 36 of theelectric motor 12, is drawn into theterminal box 34. Further, a power cable 61 (FIG. 3 ), which supplies power to afan motor 50 of thefan 14, and a signal cable 74 (FIG. 3 ), which extends from a second temperature detection section 52 (FIG. 3 ) provided in thefan 14, are drawn into theterminal box 34. It should be noted that thepower cable 61 of thefan 14 and thesignal cable 74 will be described later. - In this embodiment, the
fan 14 is installed inside therear cover 32 of theelectric motor 12, and is disposed axially rearward of thestator 24 and therotor 22, so as to be centered about the axis O. - As illustrated in
FIG. 3 , thefan 14 includes thefan motor 50, arotary body 51, and the secondtemperature detection section 52. Thefan motor 50 includes afan stator 54, afan rotor 56 rotatably arranged radially inside of thefan stator 54, and afan housing 58 that supports thefan stator 54. - A
coil 60 is wound around thefan stator 54. Thepower cable 61 is led out from thecoil 60, is wired so as to be drawn into theterminal box 34, and is electrically connected to thepower source 18. - The
fan rotor 56 includes arotary shaft 62, and arotor core 64 fixed to the radially outside of therotary shaft 62. Therotary shaft 62 is supported bybearings - The
fan housing 58 is hollow and defines an interior space S2. Thefan stator 54 and therotor core 64 are housed in the interior space S2. Thebearings fan housing 58. Therotary shaft 62 protrudes axially front ward from thefan housing 58 through a throughhole 58 b formed at an axiallyfront wall 58 a of thefan housing 58. - The
rotary body 51 includes anannular portion 70, and a plurality ofvanes 72 fixed to the radially outside of theannular portion 70. Theannular portion 70 is fixed to the axially front end of therotary shaft 62. The plurality ofvanes 72 are disposed so as to align in the circumferential direction at substantially equal intervals. - In this embodiment, the second
temperature detection section 52 is installed on thecoil 60. The secondtemperature detection section 52 has a thermocouple, a thermopile, a thermistor, or a platinum resistance temperature detector, and measures the temperature at a location at which the secondtemperature detection section 52 is installed. - The
signal cable 74 is connected to the secondtemperature detection section 52. Thesignal cable 74 is wired so as to be drawn into theterminal box 34, together with thepower cable 61 of thefan motor 50. Thesignal cable 74 is electrically connected to thecontrol device 20. The secondtemperature detection section 52 transmits information of the detected temperature to thecontrol device 20, as cooling operation information of thefan 14. - With reference to
FIG. 1 again, thepower source 18 is e.g. a commercial AC power source, and applies an AC voltage of a predetermined frequency to thecoil 60 of thefan 14, via thepower cable 61. As a result, thefan rotor 56 and therotary body 51 are rotated integrally at a predetermined rotation speed RRef. Thewarning output section 16 includes e.g. a speaker or a display, and outputs a sound or an image in accordance with a command from thecontrol device 20. - The
control device 20 controls theelectric motor 12. In this embodiment, thecontrol device 20 includes a cooling operationinformation acquisition section 76, a coolingoperation determination section 78, a runninginformation acquisition section 80, a runningcontrol section 82, a warningsignal generation section 84, and a runningdetermination section 86. - The
control device 20 may be configured by a single computer having a processor and a memory (RAM, ROM, etc.). In this case, the processor of thecontrol device 20 functions as the cooling operationinformation acquisition section 76, the coolingoperation determination section 78, the runninginformation acquisition section 80, the runningcontrol section 82, the warningsignal generation section 84, and the runningdetermination section 86. - Alternatively, the
control device 20 may be configured by a plurality of computers, each of which has a processor and a memory (RAM, ROM, etc.). In this case, the respective processors of the plurality of computers may function as the respective cooling operationinformation acquisition section 76, the coolingoperation determination section 78, the runninginformation acquisition section 80, the runningcontrol section 82, the warningsignal generation section 84, and the runningdetermination section 86. - It should be noted that the functions of the cooling operation
information acquisition section 76, the coolingoperation determination section 78, the runninginformation acquisition section 80, the runningcontrol section 82, the warningsignal generation section 84, and the runningdetermination section 86 will be described later. - Next, an operation flow of the
control device 20 will be described with reference toFIG. 4 . The flow illustrated inFIG. 4 is started when thecontrol device 20 receives an operation start command from an operator or a host controller. - At Step S1, the
control device 20 starts to run theelectric motor 12. At this time, thecontrol device 20 causes theelectric motor 12 to operate in a normal running mode. In the normal running mode, thecontrol device 20 sends a current value command I1 to theelectric motor 12, and theelectric motor 12 outputs a rotational force P1 in accordance with the current value command I1. - The current value command I1 sent by the
control device 20 in the normal running mode is set by the operator or by a computer program. In this way, thecontrol device 20 operates theelectric motor 12 in the normal running mode. - At Step S2, the
control device 20 or the operator starts to operate thefan 14. As an example, thecontrol device 20 is connected to thepower source 18 so as to control the ON/OFF of thepower source 18. In this case, at this Step S2, thecontrol device 20 transmits a command to thepower source 18 so as to turn ON thepower source 18. As another example, at this Step S2, the operator manually turns ON thepower source 18. - When the
power source 18 is turned ON, thepower source 18 supplies the AC voltage of the predetermined frequency to thecoil 60 of thefan 14. As a result, thefan 14 rotates at the predetermined rotation speed RRef, and an airflow is generated in theelectric motor 12. By this airflow, each component of theelectric motor 12 is cooled. - At Step S3, the
control device 20 starts to acquire the running information of theelectric motor 12. Specifically, thecontrol device 20 transmits a temperature detection command to the firsttemperature detection section 35 provided in theelectric motor 12. - When the first
temperature detection section 35 receives the temperature detection command, it repeatedly detects a temperature T1 at the location at which it is installed, and sequentially transmits the information of the detected temperature T1 to thecontrol device 20 via thesignal cable 39, as the running information of theelectric motor 12. - For example, the first
temperature detection section 35 may periodically measure the temperature T1 at a cycle T1 (τ1=1 [sec], for example], and sequentially transmit the temperature T1 to thecontrol device 20. Thecontrol device 20 sequentially stores in the memory the temperature T1 received from the firsttemperature detection section 35. - The temperature T1 detected at this time is one item of information indicative of the running state of the
electric motor 12 in operation (i.e., the running information). Thus, in this embodiment, thecontrol device 20 functions as the running information acquisition section 80 (FIG. 1 ) configured to acquire the running information of theelectric motor 12. - At Step S4, the
control device 20 starts to acquire the cooling operation information of thefan 14. Specifically, thecontrol device 20 transmits a temperature detection command to the secondtemperature detection section 52 provided in thefan 14. - When the second
temperature detection section 52 receives the temperature detection command, it repeatedly detects a temperature T2 at the location at which it is installed, and sequentially transmits the information of the detected temperature T2 to thecontrol device 20 via thesignal cable 74, as the cooling operation information of thefan 14. - For example, the second
temperature detection section 52 may periodically measure the temperature T2 at a cycle τ2 (τ2=1 [sec], for example), and sequentially transmit the temperature T2 to thecontrol device 20. Thecontrol device 20 sequentially stores in the memory the temperature T2 received from the secondtemperature detection section 52. - The temperature T2 detected at this time is one item of the information indicative of the cooling operation state of the working
fan 14 in operation (i.e., the cooling operation information). More specifically, as theelectric motor 12 operates, the rotation of therotary body 51 or thefan rotor 56 of thefan 14 may possibly be obstructed, due to which, the rotation speed of thefan 14 may decrease from the rotation speed RRef. - Such obstruction of the rotation of the
rotary body 51 or thefan rotor 56 may be caused e.g. by a foreign material, such as cutting fluid, attaching to therotary body 51 or thefan rotor 56 during operation of theelectric motor 12. - If the rotation speed of the
fan 14 decreases, the load on thefan motor 50 increases, as a result of which, the temperature of thefan motor 50 rises. On the other hand, the airflow generated in theelectric motor 12 decreases, as a result of which the performance of thefan 14 to cool theelectric motor 12 deteriorates. - In this way, since there is a high correlation between the temperature T2 detected by the second
temperature detection section 52 and the cooling operation state of thefan 14, the temperature T2 can be used as the cooling operation information of thefan 14. Thus, in this embodiment, thecontrol device 20 functions as the cooling operation information acquisition section 76 (FIG. 1 ) configured to acquire the cooling operation information of thefan 14. - At Step S5, the
control device 20 determines whether or not the cooling operation information of thefan 14 indicates a normal cooling operation. Specifically, thecontrol device 20 determines whether or not the temperature T2 most-recently acquired from the secondtemperature detection section 52 is lower than a threshold value T2α (i.e., T2<T2α). - The threshold value T2α is predetermined by the operator, and is stored in the memory of the
control device 20. When T2<T2α is satisfied, thecontrol device 20 determines that the cooling operation information of thefan 14 indicates the normal cooling operation (i.e., determines YES), and proceeds to Step S6. - On the other hand, when T2 is equal to or greater than the threshold value T2α, (i.e., T2≥T2α), the
control device 20 determines that the cooling operation information of thefan 14 does not indicate the normal cooling operation (i.e., determines NO), and proceeds to Step S7. Thus, in this embodiment, thecontrol device 20 functions as the cooling operation determination section 78 (FIG. 1 ) configured to determine whether or not the cooling operation information indicates the normal cooling operation. - At Step S6, the
control device 20 determines whether or not it receives an operation end command from the operator or the host controller. If thecontrol device 20 determines that it receives the operation end command (i.e., determines YES), thecontrol device 20 transmits a stop command to theelectric motor 12, sets the current value supplied to theelectric motor 12 to zero. Thereby, the operation of theelectric motor 12 is stopped. - Further, if the
control device 20 is connected to thepower source 18 so as to control the ON/OFF of thepower source 18, thecontrol device 20 turns OFF thepower source 18 and stops the cooling operation of thefan 14. Then, thecontrol device 20 ends the flow illustrated inFIG. 4 . On the other hand, if thecontrol device 20 determines that it does not receive the operation end command (i.e., determines NO), thecontrol device 20 returns to Step S5. - At Step S7, the
control device 20 notifies to the operator via thewarning output section 16 that an abnormality occurs in the cooling operation of thefan 14. Specifically, thecontrol device 20 generates the warning signal in the form of a voice signal or an image signal. Then, thecontrol device 20 transmits the generated warning signal to thewarning output section 16. - The
warning output section 16 outputs the warning sound or the warning image in accordance with the received warning signal via the speaker or the display portion. In this way, the operator can recognize that an abnormality has occurred in the cooling operation of thefan 14. Thus, in this embodiment, thecontrol device 20 functions as the warning signal generation section 84 (FIG. 1 ) configured to generate the warning signal. - At Step S8, the
control device 20 determines whether or not the running information of theelectric motor 12 indicates the normal running of theelectric motor 12. Specifically, thecontrol device 20 determines whether or not the temperature T1 most-recently acquired from the firsttemperature detection section 35 is lower than a threshold value T1α, (i.e., T1<T1α). - The threshold value T1α is predetermined by the operator, and is stored in the memory of the
control device 20. For example, the threshold value T1α is set as a threshold value defining a boundary to determine whether theelectric motor 12 is in an overheated state. In this case, when the temperature T1 is equal to or greater than the threshold value T1α, (i.e., T1≥T1α), theelectric motor 12 is considered to be overheating. - When T1<T1α is satisfied, the
control device 20 determines that the running information of theelectric motor 12 indicates the normal running (i.e., determines YES), and proceeds to Step S10. On the other hand, when T1≥T1α is satisfied, thecontrol device 20 determines that the running information of theelectric motor 12 does not indicate normal running (i.e., determines NO), and proceeds to Step S9. - Thus, in this embodiment, the
control device 20 functions as the running determination section 86 (FIG. 1 ) configured to determine whether the running information of theelectric motor 12 indicates normal running. - At Step S9, the
control device 20 stops the operation of theelectric motor 12. Specifically, thecontrol device 20 transmits the stop command to theelectric motor 12, and sets the current value supplied to theelectric motor 12 to zero. In this way, the operation of theelectric motor 12 is stopped. Then, thecontrol device 20 ends the flow illustrated inFIG. 4 . - At Step S10, the
control device 20 acquires first data indicating a possibility that theelectric motor 12 is in an overheated state. Below, the technical significance of the first data will be explained with reference toFIG. 6 . - A one-
dot chain line 90 inFIG. 6 indicates a relationship between a time t and the temperature T1 when the cooling operation of thefan 14 is normal and theelectric motor 12 is run at a rated current value. In thisrelationship 90, after theelectric motor 12 starts to run, the temperature T1 increases with time and approaches asymptotically to a predetermined saturation temperature T1 (<T1α). - A two-
dot chain line 92 inFIG. 6 indicates a relationship between the time t and the temperature T1 when an abnormality occurs in the cooling operation of thefan 14 but theelectric motor 12 is run at a current value that is significantly smaller than the rated current value. In thisrelationship 92, the temperature T1 of theelectric motor 12 reaches saturation at a temperature that is significantly lower than the saturation temperature T1β. - On the other hand, a
broken line 94 inFIG. 6 indicates a relationship between the time t and the temperature T1 when an abnormality occurs in the cooling operation of thefan 14 at a time point t1 during thefan 14 is run at the rated current value, and theelectric motor 12 continues to be run at the rated current value even after the abnormality occurs. - In this
relationship 94, after theelectric motor 12 begins running, the temperature T1 rapidly increases and exceeds the saturation temperature T1β and the overheat temperature T1α (i.e. the above-described threshold value T1α). In this case, theelectric motor 12 is in an overheated state. - In this embodiment, at Step S10, the
control device 20 acquires the first data in order to quantitatively evaluate the possibility that the running of theelectric motor 12 is in an overheated state. As an example, thecontrol device 20 calculates, as the first data, a difference δ1 (=T1α−T1) between the most-recently acquired temperature T1 and the overheat temperature T1α. - The smaller this difference δ1, the greater the possibility of the
electric motor 12 being an overheated state, and therefore the difference δ1 can be used as the first data δ1 indicating the possibility that the running of theelectric motor 12 is in an overheated state. - As another example, the
control device 20 calculates a degree of increase of the temperature T1 with respect to the time t, as the first data. For example, using a temperature T1(n) most-recently acquired from the firsttemperature detection section 35, a temperature T1(n-1) acquired from the firsttemperature detection section 35 immediately before the temperature T1(n), and the measurement cycle τ1, thecontrol device 20 calculates a degree of increase δT1/δt (=(T1(n)−T1(n-1))/τ). - This degree of increase δT1/δt corresponds to a gradient of the graph shown in
FIG. 6 . With reference toFIG. 6 , it can be seen that the gradient of therelationship 94 is significantly greater than theother relationships electric motor 12 is in an overheated state. - As a further example, the
control device 20 may calculate both δ1 and δT1/δt as the first data. In this way, thecontrol device 20 acquires the first data (δ1, δT1/δt) and stores it in the memory. - At Step S11, on the basis of the first data (δ1, δT1/δt) acquired at Step S10, the
control device 20 determines whether or not the possibility that the running of theelectric motor 12 is in an overheated state is high. - As an example, when the first data δ1 (=T1α−T1) is calculated at Step S10, at this Step S11, the
control device 20 determines whether or not the first data δ1 is equal to or less than a threshold value α (i.e., δ1≤α). The threshold value α is predetermined by the operator, and is stored in the memory of thecontrol device 20. - When δ1≤α is satisfied, the
control device 20 determines that the possibility that the running of theelectric motor 12 is in an overheated state is high (i.e., determines YES), and proceeds to Step S12. On the other hand, when δ1<α is satisfied, thecontrol device 20 determines that the possibility that the running of theelectric motor 12 is in an overheated state is low (i.e., determines NO), returns to the above-described Step S6, and continues running theelectric motor 12 in the normal running mode until it determines YES at Step S6. - As another example, when the first data δT1/δt (=(T1(n)−T1(n-1))/τ) is calculated at Step S10, at this Step S11, the
control device 20 determines whether or not the first data δT1/δt is equal to or greater than a threshold value β (i.e., δT1/δt≥β). The threshold value β is predetermined by the operator, and is stored in the memory of thecontrol device 20. - The
control device 20 determines YES when δT1/δt≥β is satisfied, and proceeds to Step S12. On the other hand, thecontrol device 20 determines NO when δT1/δt<β is satisfied, and returns to the above-described Step S6. - As yet another example, when both δ1 and δT1/δt are acquired as the first data at Step S10, the
control device 20 may determine the possibility of theelectric motor 12 being in an overheated state, on the basis of δ1 and δT1/δt. For example, thecontrol device 20 may determine YES when δ1≤α or δT1/δt≥β, while determining NO when δ1<α and δT1/δt<β. - At Step S12, the
control device 20 runs theelectric motor 12 in an abnormal running mode. This Step S12 will be described with reference toFIG. 5 . After beginning Step S12, at Step S21, thecontrol device 20 reduces the output of theelectric motor 12. - Specifically, the
control device 20 changes the current value command transmitted to theelectric motor 12 from the current value command I1 to a second current value command I2, and sends the second current value command I2 to theelectric motor 12. The second current value command I2 is for running theelectric motor 12 at a lower current value than the current value command I1. As a result, theelectric motor 12 outputs a second rotational force P2 (<P1) in accordance with the second current value command I2. - At Step S22, the
control device 20 acquires second data in order to quantitatively evaluate a possibility that the temperature T1 of theelectric motor 12 exceeds the saturation temperature T1β. As an example, thecontrol device 20 calculates, as the second data, a difference δ2 (=T1β−T1) between the most-recently acquired temperature T1 and the saturation temperature T1β. - The smaller this difference δ2, the greater the possibility of the temperature T1 exceeding the saturation temperature T1β, and therefore the difference δ2 can be used as the second data δ2 indicating the possibility that the temperature T1 exceeds the saturation temperature T1β.
- As another example, the
control device 20 calculates the degree of increase δT1/δt (=(T1(n)−T1(n-1))/τ) of the temperature T1 with respect to time, as the second data. As yet another example, thecontrol device 20 may calculate both δ2 and δT1/δt as the second data. Thecontrol device 20 acquires the second data (δ2, δT1/δt) and stores it in the memory. - At Step S23, on the basis of the second data (δ2, δT1/δt) acquired at Step S22, the
control device 20 determines whether or not the possibility that the temperature T1 exceeds the saturation temperature T1β is high. - As an example, when the second data δ2 (=T1β−T1) is calculated at Step S22, at this Step S23, the
control device 20 determines whether or not the second data δ2 is equal to or less than a threshold value γ (i.e., δ2≤γ). The threshold value γ is predetermined by the operator, and is stored in the memory of thecontrol device 20. - When δ2≤γ is satisfied, the
control device 20 determines that the possibility of the temperature T1 exceeding the saturation temperature T1β is high (i.e., determines YES), and returns to Step S21. On the other hand, when δ2>γ is satisfied, thecontrol device 20 determines that the possibility of the temperature T1 exceeding the saturation temperature T1β is low (i.e., determines NO), and proceeds to Step S24. - As another example, when the second data δT1/δt is calculated at Step S22, at this Step S23, the
control device 20 determines whether or not the second data δT1/δt is equal to or greater than a threshold value ε (i.e., δT1/δt≥ε). The threshold value ε is predetermined by the operator, and is stored in the memory of thecontrol device 20. It should be noted that the threshold value ε may be the same as or different from the above-described threshold value β. - The
control device 20 determines YES when δT1/δt≥ε is satisfied, and returns to Step S21. On the other hand, thecontrol device 20 determines NO when δT1/δt<ε is satisfied, and proceeds to Step S24. - As yet another example, when both δ2 and δT1/δt are acquired as the second data at Step S21, the
control device 20 may determine the possibility of the temperature T1 exceeding the saturation temperature T1β on the basis of δ2 and δT1/δt. For example, thecontrol device 20 may determine YES when δ2≤γ or δT1/δt≥ε, while determining NO when δ2>γ and δT1/δt<ε. - In this way, the
control device 20 repeats Step S21 to Step S23 until it determines NO at Step S23. Thecontrol device 20 reduces the output of theelectric motor 12 in a stepwise manner each time thecontrol device 20 executes Step S21. - Specifically, the
control device 20 changes the current value command transmitted to theelectric motor 12 from an mth current value command Im to an (m+1)th current value command Im+1, and sends to theelectric motor 12. The (m+1)th current value command Im+1 is for running theelectric motor 12 at a current value lower than the mth current value command Im. As a result, theelectric motor 12 outputs an (m+1)th rotational force Pm+1 (<Pm) in accordance with the (m+1)th current value command Im+1. - Such a running control of the
electric motor 12 will be described with reference toFIG. 7 . Asolid line 96 inFIG. 7 indicates a relationship between the temperature T1 and the time t when theelectric motor 12 is run in the abnormal running mode. A solid line 98 inFIG. 7 indicates a relationship between the current value I and the time t when theelectric motor 12 is run in the abnormal running mode. Further, inFIG. 7 , for comparison, therelationships FIG. 6 are also shown. - At a time point t2, the
control device 20 reduces the current value I of theelectric motor 12 from the current value I1 to the current value I2 (carrying out Step S21 for a first time). Then, at a time point t3, thecontrol device 20 further reduces the current value I of theelectric motor 12 from the current value I2 to a current value I3 (carrying out Step S21 for a second time). - In this way, the
control device 20 controls the current value I of theelectric motor 12 with reference to the temperature T1 and the saturation temperature T1β. Due to this, as shown by therelationship 96 inFIG. 7 , the temperature T1 of theelectric motor 12 approaches asymptotically to the saturation temperature T1β so as not to exceed the saturation temperature T1β, as a result of which, overheating by exceeding the saturation temperature T1α is prevented. - Thus, in this embodiment, the
control device 20 functions as the running control section 82 (FIG. 1 ) configured to control the running of theelectric motor 12 with reference to the running information (the temperature T1) so as to be in an overheat-prevented state. - At Step S24, similarly to the above-described Step S6, the
control device 20 determines whether it receives the operation end command. When thecontrol device 20 determines YES, thecontrol device 20 stops the running of the electric motor 12 (and the power source 18), ends Step S12 illustrated inFIG. 5 , and thus ends the flow illustrated inFIG. 4 . On the other hand, when thecontrol device 20 determines NO, thecontrol device 20 returns to step S23. - As described above, in this embodiment, the
control device 20 controls the running of theelectric motor 12 so as to be in the overheat-prevented state with reference to the running information (the temperature T1) of theelectric motor 12, when thecontrol device 20 determines that the cooling operation information (the temperature T2) of thefan 14 does not indicate the normal cooling operation (i.e., determines NO at Step S5). - According to this configuration, even when an abnormality occurs in the cooling operation of the
fan 14, the running of theelectric motor 12 can be continued so as not to become overheated. As a result, it is possible to avoid completely stopping an operation (e.g., machining) using theelectric motor 12, and the operator can repair or replace thefan 14 at a desired timing that will not obstruct the operation. - Further, in this embodiment, when the
control device 20 determines NO at Step S5, thecontrol device 20 generates the warning signal for notifying the abnormality in the cooling operation of thefan 14, and notifies the operator. According to this configuration, the operator can reliably recognize that an abnormality has occurred in thefan 14. - Further, in this embodiment, the
control device 20 acquires the temperature T2 detected by the secondtemperature detection section 52 as the cooling operation information of thefan 14. As described above, since there is a high degree of correlation between the temperature T2 and the cooling operation state of thefan 14, thecontrol device 20 can determine whether the cooling operation of thefan 14 is normal with using the temperature T2 in a quantitative and highly accurate manner, at Step S5. - In addition, in this embodiment, the
control device 20 determines whether the running information (the temperature T1) of theelectric motor 12 is normal (Step S8), and thecontrol device 20 stops the operation of the electric motor 12 (Step S9) if it determines that the running information is not normal (i.e., determines NO at Step S8). According to this configuration, overheating of theelectric motor 12 can be reliably detected, and it is possible to immediately stop the operation of theelectric motor 12. - Further, in this embodiment, by executing the above-described Step S21 to Step S23, the
control device 20 controls the operation of theelectric motor 12 such that the temperature T1 of theelectric motor 12 does not exceed the saturation temperature T1β. - According to this configuration, the
electric motor 12 can be reliably prevented from overheating, and the output of theelectric motor 12 can be increased to a maximum within a range in which the overheat-prevented state of theelectric motor 12 is maintained. Thus, even when an abnormality occurs in thefan 14, it is possible to maximize work efficiency. - Further, in this embodiment, the
control device 20 carries out the abnormal running mode at Step S12 only when it determines YES at Step S11. According to this configuration, it is possible to control theelectric motor 12 so as to be in the overheat-prevented state at Step S12 when the possibility of theelectric motor 12 being in the overheated state is high. On the other hand, theelectric motor 12 can be operated in the normal running mode such that the output of theelectric motor 12 can be prevented from decreasing excessively when the possibility of the overheated state is low (e.g., in the case of therelationship 92 inFIG. 6 ). - Next, an
electric motor system 100 according to another embodiment will be described with reference toFIG. 8 . Theelectric motor system 100 is different from the above-describedelectric motor system 10 in afan 102. Thefan 102 according to this embodiment is different from the above-describedfan 14 in that thefan 102 includes arotation detection section 104 instead of the secondtemperature detection section 52. - The
rotation detection section 104 includes e.g. an encoder or a Hall element, and measures the rotation speed of thefan 102. Specifically, therotation detection section 104 is disposed in the vicinity of thefan rotor 56 or therotary body 51 of thefan 102, and measures the rotation speed of thefan rotor 56 or therotary body 51. Therotation detection section 104 transmits, as cooling operation information of thefan 102, the information of the detected rotation speed to thecontrol device 20 via thesignal cable 74. - Next, an operation flow of the
electric motor system 100 will be described with reference toFIG. 4 andFIG. 5 . Thecontrol device 20 of theelectric motor system 100 carries out the operation flow illustrated inFIG. 4 andFIG. 5 . The operation flow of theelectric motor system 100 differs from the above-described embodiment in Steps S4 and S5. - At Step S4, the
control device 20 functions as the cooling operationinformation acquisition section 76, and starts to acquire the cooling operation information of thefan 102. Specifically, thecontrol device 20 transmits a rotation detection command to therotation detection section 104 provided in thefan 102. - When the
rotation detection section 104 receives the rotation detection command, therotation detection section 104 repeatedly (e.g., at a cycle τ3) measures a rotation speed R of thefan 102, and sequentially transmits, as the cooling operation information of thefan 102, the information of the detected rotation speed R to thecontrol device 20 via thesignal cable 74. Thecontrol device 20 sequentially stores the rotation speed R received from therotation detection section 104 in the memory. - Since the rotation speed R of the
fan 102 is proportional to the airflow generated by thefan 102 in theelectric motor 12, there is a high correlation between the rotation speed R and the cooling operation state of thefan 102. Therefore, the rotation speed R can be used as the information indicating the cooling operation state of the working fan 102 (i.e., the cooling operation information). - At Step S5, the
control device 20 functions as the coolingoperation determination section 78, and determines whether or not the cooling operation information of thefan 102 indicates the normal cooling operation. Specifically, thecontrol device 20 determines whether or not the rotation speed R most-recently acquired from therotation detection section 104 is higher than a threshold value Rα (i.e., R>Rα). - The threshold value Rα is predetermined by the operator as a value lower than the above-described rotation speed RRef (i.e., Rα>RRef), and is stored in the memory of the
control device 20. When R>Rα is satisfied, thecontrol device 20 determines that the cooling operation information of thefan 102 indicates the normal cooling operation (i.e., determines YES), and proceeds to Step S6. - On the other hand, when R is equal to or less than the threshold value Rα, (i.e., R≤Rα), the
control device 20 determines that the cooling operation information of thefan 102 does not indicate the normal cooling operation (i.e., determines NO), and proceeds to Step S7. After Step S5, thecontrol device 20 sequentially carries out Step S6 to Step S12, similarly as the above-described embodiment. - In this embodiment, the
control device 20 acquires the rotation speed R detected by therotation detection section 104 as the cooling operation information of thefan 102. As described above, since there is a high degree of correlation between the rotation speed R and the cooling operation state of thefan 102, thecontrol device 20 can determine whether the cooling operation of thefan 102 is normal with using the rotation speed R in a quantitative and highly accurate manner, at Step S5. - It should be noted that the warning
signal generation section 84 and the runningdetermination section 86 can be omitted from the above-describedcontrol device 20. Such acontrol device 110 is illustrated inFIG. 9 . Thecontrol device 110 includes a cooling operationinformation acquisition section 112, a coolingoperation determination section 114, a runninginformation acquisition section 116, and a runningcontrol section 118. - The
control device 110 can be configured by a single computer having a processor and a memory (RAM, ROM, etc.). In this case, the processor of thecontrol device 110 functions as the cooling operationinformation acquisition section 112, the coolingoperation determination section 114, the runninginformation acquisition section 116, and the runningcontrol section 118. - Alternatively, the
control device 110 may be configured by a plurality of computers, each having a processor and a memory (RAM, ROM, etc.). In this case, the respective processors of the plurality of computers may functions as the respective cooling operationinformation acquisition section 112, the coolingoperation determination section 114, the runninginformation acquisition section 116, and the runningcontrol section 118. - The cooling operation
information acquisition section 112 acquires the cooling operation information of thefan 14, 102 (e.g., the temperature T2 or the rotation speed R). The coolingoperation determination section 114 determines whether or not the cooling operation information indicates the normal cooling operation. For example, similarly to the above-described embodiment, the coolingoperation determination section 114 determines whether the cooling operation information indicates the normal cooling operation by comparing the cooling operation information with a predetermined threshold value. - The running
information acquisition section 116 acquires the running information (e.g., the temperature T1) of theelectric motor 12. When the coolingoperation determination section 114 determines that the cooling operation information does not indicate the normal cooling operation, the runningcontrol section 118 controls the running of theelectric motor 12 so as to be in the overheat-prevented state with reference to the running information acquired by the runninginformation acquisition section 116. - For example, similar to the above-described embodiment, the running
control section 118 controls the running of theelectric motor 12 to be in the overheat-prevented state by reducing the output (e.g., the current value) of theelectric motor 12 with reference to the running information. - According to this embodiment, if an abnormality occurs in the cooling operation of the
fan electric motor 12 so as not to overheat. As a result, it is possible to avoid completely stopping an operation using theelectric motor 12, and the operator can repair or replace thefan - It should be noted that the above-described first
temperature detection section 35 may be disposed at any location in theelectric motor 12. Further, the firsttemperature detection section 35 of theelectric motor 12 may be omitted, wherein the cooling operationinformation acquisition section electric motor 12, a feedback (a feedback current, a load torque, etc.) of theelectric motor 12, instead of the above-described temperature T1. In this case, at Step S8, thecontrol device electric motor 12 is normal (i.e., whether it is in an overheated state). - This threshold value ζ can be set as a feedback transmitted from the
electric motor 12 when theelectric motor 12 is in the overheated state. Further, in this case, at Step S10 and Step S22, thecontrol device electric motor 12. - In addition, the
power source 18 may not necessarily be a commercial AC power source, and may be a power source having an inverter therein, which is capable of controlling the frequency. - Further, in the above-described embodiment, the
warning output section 16 is provided separate from thecontrol device 20, but may alternatively be incorporated in thecontrol device 20. In this case, thecontrol device 20 may include the display or the speaker. - Further, the
control device electric motor 12 after Step S23 inFIG. 5 . Further, thecontrol device electric motor 12, instead of the current value command I. In this case, thecontrol device FIG. 5 . - In addition, in the above-described embodiment, the
fan 14 is installed inside therear cover 32 axially rearward of thestator 24 and therotor 22 of theelectric motor 12. - However, the
fan 14 may be installed at any position where thefan 14 can cool theelectric motor 12. Further, thefan 14 is not limited to the axial fan illustrated inFIG. 3 , but may be any type of fan, such as a centrifugal fan, which can generate an airflow. - While the present disclosure has been described through the embodiments, the above-described embodiments do not limit the disclosure according to the claims.
Claims (9)
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JP2017122290A JP6469174B2 (en) | 2017-06-22 | 2017-06-22 | Electric motor control device, electric motor system, and electric motor control method |
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US20180375460A1 true US20180375460A1 (en) | 2018-12-27 |
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Citations (3)
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US6291959B1 (en) * | 1999-03-24 | 2001-09-18 | Makino Milling Machine Co., Ltd. | Method and apparatus for controlling numerically controlled machine tool |
US8330586B2 (en) * | 2009-02-24 | 2012-12-11 | Marvell World Trade Ltd. | Systems and methods for programming of a cooling fan via a serial port communication mode |
US10042346B2 (en) * | 2014-03-03 | 2018-08-07 | Fanuc Corporation | Numerical control device provided with heat radiation characteristic estimation part |
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JP2005080384A (en) * | 2003-08-29 | 2005-03-24 | Calsonic Kansei Corp | Electric fan control unit |
JP5893535B2 (en) * | 2012-09-11 | 2016-03-23 | 東芝三菱電機産業システム株式会社 | Electric motor preventive maintenance device, electric motor preventive maintenance method, and electric motor preventive maintenance system |
JP5616413B2 (en) | 2012-10-04 | 2014-10-29 | ファナック株式会社 | Motor control device used by switching the PWM frequency |
DE102013202434A1 (en) | 2013-02-14 | 2014-08-28 | Robert Bosch Gmbh | Method and device for limiting a power consumption of an electric motor in case of overload in a hand tool |
JP6174626B2 (en) | 2015-06-01 | 2017-08-02 | ファナック株式会社 | Motor driving apparatus and method capable of notifying flow abnormality of fluid flowing in heat sink |
JP6312645B2 (en) * | 2015-10-09 | 2018-04-18 | ファナック株式会社 | Motor driving apparatus capable of reporting abnormal operation of fan and method thereof |
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2017
- 2017-06-22 JP JP2017122290A patent/JP6469174B2/en active Active
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Patent Citations (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US6291959B1 (en) * | 1999-03-24 | 2001-09-18 | Makino Milling Machine Co., Ltd. | Method and apparatus for controlling numerically controlled machine tool |
US8330586B2 (en) * | 2009-02-24 | 2012-12-11 | Marvell World Trade Ltd. | Systems and methods for programming of a cooling fan via a serial port communication mode |
US10042346B2 (en) * | 2014-03-03 | 2018-08-07 | Fanuc Corporation | Numerical control device provided with heat radiation characteristic estimation part |
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CN109120209A (en) | 2019-01-01 |
JP2019009877A (en) | 2019-01-17 |
DE102018114371B4 (en) | 2022-10-27 |
JP6469174B2 (en) | 2019-02-13 |
CN109120209B (en) | 2020-02-07 |
US10536106B2 (en) | 2020-01-14 |
DE102018114371A1 (en) | 2018-12-27 |
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